As computers have become more complex, user interfaces have had to adapt to allow the user to control the operations of the computer. Initially, the interface used was a command line interface, which utilized a series of typed commands formatted in a specific syntax familiar to the computer and eventually learned by computer users. This interface was eventually replaced by the Graphical User Interface (“GUI”), which allows users to point to objects, buttons, and windows displayed like items on a desk. Interaction between the GUI and a user is accomplished through a display and user interface selection device. Initially, the user interface selection device was a light pen, a pen-based computer control requiring the user to select and highlight objects on the screen by touching the light to the object on the screen. However, this implementation had its disadvantages because, by design, the user's hands and the light pen would obscure a portion of the screen from the user's own view. This and other disadvantages led to the development of the mouse, an interface control separate from the keyboard that controlled a pointer on the GUI for selecting and highlighting objects, buttons, and windows.
Current methods available for text input and desktop environment navigation through a user interface selection device into a computing system are associated with at least one of several disadvantages. Although keyboards allow for fast textual input, they are extremely cumbersome for navigating through a desktop environment. Similarly, although a mouse is ideal for navigating through a desktop environment, it is not a good text-input solution. Likewise, joysticks and conventional laptop touchpads allow for fast navigation, but are cumbersome textual input devices. Most conventional systems alleviate the aforementioned problems by a combination of a keyboard and a mouse, touchpad, or joystick. However, this implementation introduces another significant obstacle of requiring two-hand operation of the user interface.
The growth of the personal digital assistant (“PDA”) and wearable computer markets are associated with similar problems realized in the larger-scale computing systems. As PDA technology continues to rapidly advance with respect to the size of PDA electronics and batteries, the size of the handheld and mobile devices becomes more dependent upon the input devices used.
The current most practiced method of interaction between a user and a PDA is through the use of a stylus. In stylus-based interaction, the user holds the device in one hand and the stylus in the other. While such interaction is similar to the use of a conventional pad and paper, it is not without disadvantages. First, it requires two-hand operation. Second, complex software algorithms are typically needed to recognize the user's handwriting. Third, stylus-based interaction requires the user to look at the device while using it. Other methods of interaction, such as the 9-Key method commonly used in cellular telephones and voice recognition, are characterized by any one of the above-mentioned disadvantages.